Reviving a Vintage Transmission Electron Microscope - The Philips EM 420 Part 4, Inside Some Penning Gauges, and More Vacuum Problems.

Figure 1 - 60s vintage Glass Penning Gauge, complete with holder and magnets (black discs).

So currently the scope is stuck on low vacuum, basically only pumping the lines, not even the ODP or Buffer Tank. I can manually, using a jumper force the valves (V1) between RVP and the Buffer Tank to open, and V2 on the ODP to open. It reaches a satisfactory vacuum on the Buffer Tank which should enable the Oil Diffusion Pump heater to turn on. However it is not, and I do not hear its relay clicking over so I will jump around and check a few things, first the ODP fuse, then power to the pump heater relay coil, and probably several other things I suspect in the circuit. I am leaning heavy towards the some of the Vacuum Control PCBs.

In short V1 and V2 wont open, ODP heater does not turn on.

Also, hours spent on this TEM so far.

Fabricate plinths, lift scope, move and lower : 3 hrs
Connect power unit and 40 Amp L630 plug : 1 hr
Instal Pirani gauge on lines, and Penning on ODP
Connect water and air, monitor pumping : 1.5 hrs
Check, replace faulty buffer tank pirani gauge: : 0.5 hrs

I have actually spent more time writing all this stuff and finding good references then doing the actual work. So...Please Upvote! HA!

BAck to Penning gauges...here I have a Edwards CP2, much like a CP25 break down, as well as an older 60s vintage glass gauge, which has NEVER been used. I am actually thinking about hanging this off part of the stage, also known as the Octagon, and hooking up a analog meter. Been thinking about the fastest way to do this. Perhaps by the time this is running I will have an elegant way to knock it out. It will require machining vacuum adapters, lead casting, making or modifying a power supply etc. Nothing new to me ;-) I posted about the octagon from a 90s or 2000s CM20 or similar months back. It is essentially identical to the 420, you can see it here: Octagon, Pole Piece, Anti-Contamination Device

As promised:

Figure 2: Looking down a Edwards CP2 penning tube from the vacuum interface side

Figure 3: Edwards CP2 from the side.

Figure 4: Plug unscrewed in back and baskets that sit on Cathode plate and spring carefully poured onto my desk ;-) The magnet in this Penning Gauge encircle the baskets, inside the red shroud

Figure 5: Here you can see the arrangement of the baskets, not sure how much it matters that two are open to each other, but I always put them back the same way I find them.

Figure 6: The blue material is glass fused to the Anode and Cathode plate. It can crack.

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Figure 7: Close up of the old penning tube. The two plates are Platinum. I think I have a picture of one of these in operation somewhere, it looks really cool. They like to glow blue if I remember correctly.

So looking over things I found that the HV supply for the Penning gauge was not plugged in completely, which is part of the problem. Also, a Vacuum connection on the buffer tank is cracked severely, however unrelated to the problems I have now. I will replace it before the next post. See below.

Figure 8: Cracked vacuum connector on Buffer Tank.

Allright, all the suspect things I mentioned earlier, besides PCBs check out so I am thinking something has gone awry on a PCB. The more I think of it, the more it makes sense. I want to give this a few good hours tomorrow, so hopefully you all will see another update real soon. Alright...im falling asleep. Ha!